B6 - Biofuels

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  • Created by: Naomi
  • Created on: 21-01-13 13:01
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  • Biofuels
    • Green plants use light energy from the sun to photosynthesise
      • Photosynthesis produces energy and plants use the energy to grow and gain mass
        • The mass of plants is called biomass. The energy that is trapped in biomass can be used to make biofuels
    • Biogas
      • Biogas is a fuel that contains
        • Mainly methane
        • Some carbon dioxide
        • Very samll amounts of hydrogen, nitrogen and hydrogen sulphide
      • Biogas can be made on a large scale in a digester
        • This uses a continuous flow method as organic wastes are constantly added and the gas and remaining solids are constantly removed
      • The biogas that is made is:
        • Burnt to generate electricity
        • Burnt to produce hot water and steam for heating systems
        • Used as fuel for vehicles
      • Biogas production is affected by temperature because as the temperature increases, the bacteria multiply faster and the enzymes within them work better
        • Above 45 degrees, the enzymes are denatured and the bacteria die
    • Ways to make biofuels
      • Fast growing trees are grown and the wood is burnt
      • Biomass such as sugar or waste material is fermented using bacteria or yeast and the product is used as fuel
        • Alcohol is made by fermtation and is mixed with petrol to make gasohol
          • This is used to make petrol
          • Gasohol is an ideal fuel where there is ample sugar cane but little oil
    • Gasohol
      • Alcohol is made by fermtation and is mixed with petrol to make gasohol
        • This is used to make petrol
        • Gasohol is an ideal fuel where there is ample sugar cane but little oil
    • Advantages and disadvantages of biofuels
      • Advantages
        • Much cleaner fuel than fossil fuels
        • Using biofuels means that fossil fuels will last longer
        • Biofules do not increase the net levels of carbon dioxide in the air
          • Called carbon-neutral if they are burnt at the same rate as the biomass is being produced
        • They do not release particulates when they are burnt
      • Disadvantages
        • It destroys large ares of natural habitat to grow the biomass
        • It contains less energy than other fossil fuels

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